/*
 * Copyright (C) 2012 CyberAgent
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package cn.jarlen.photoedit.filter.single;

import cn.jarlen.photoedit.filter.base.GPUImageFilter;

/**
 * Applies a grayscale effect to the image.
 */
public class GPUImageGrayscaleFilter extends GPUImageFilter
{
	public static final String GRAYSCALE_FRAGMENT_SHADER = ""
			+ "precision highp float;\n"
			+ "\n"
			+ "varying vec2 textureCoordinate;\n"
			+ "\n"
			+ "uniform sampler2D inputImageTexture;\n"
			+ "\n"
			+ "const highp vec3 W = vec3(0.2125, 0.7154, 0.0721);\n"
			+ "\n"
			+ "void main()\n"
			+ "{\n"
			+ "  lowp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);\n"
			+ "  float luminance = dot(textureColor.rgb, W);\n" + "\n"
			+ "  gl_FragColor = vec4(vec3(luminance), textureColor.a);\n" + "}";

	public GPUImageGrayscaleFilter()
	{
		super(NO_FILTER_VERTEX_SHADER, GRAYSCALE_FRAGMENT_SHADER);
	}
}
